1. Field of the Invention
This disclosure relates in general to air bearing pads for magnetic storage devices, and more particularly to a method and apparatus for providing a three step air bearing with improved fly height performance
2. Description of Related Art
Fixed magnetic storage systems are now commonplace as a main non-volatile storage in modern personal computers, workstations, and portable computers. Storage systems are now capable of storing gigabyte quantities of digital data, even when implemented in portable computers.
Magnetic recording systems that utilize magnetic disk and tape drives constitute the main form of data storage and retrieval in present-day computer and data processing systems. Many important advances have been made that provide higher data density and thus increased storage capacities for storage systems. These advances include faster access speeds and faster access times resulting in a greater bandwidth of data communicated to and from the storage systems. Advances have also been made by greatly reducing the size and weight of the storage systems, resulting in the availability of ultra-light portable computers having state-of-the art capabilities and performance.
A disk drive is one example of a magnetic storage system. A disk drive storage system, for example, uses a rotatable disk with concentric data tracks containing information, a head for reading and/or writing data onto the various tracks, and an actuator connected to a sensor for moving the sensor to a desired track and maintaining the sensor over the track centerline during read and write operations. The sensor is suspended in close proximity to a recording medium. For example, the sensor may be suspended over a magnetic disk having a plurality of concentric tracks. Another type of magnetic storage system includes a magnetic tape system. However, storage systems are not limited merely to the above-mentioned magnetic storage systems.
Disk drive storage systems utilize thin film head designs that are mostly variations of a merged design or a piggyback design. The merged design, as well as the piggyback design, places a write element atop a read sensor. In these dual-element designs, an inductive coil element used for writing and a magnetoresistive (MR) element used for reading are spaced apart from one another in a direction perpendicular to the trailing end of the merged head.
In the recording process, information is written and stored as magnetization patterns on the magnetic recording medium. Scanning a write head over the medium and energizing the write head with appropriate current waveforms accomplish this recording process. In a read-back process, scanning a magnetoresistive (MR) sensor over the medium retrieves the stored information. This MR read head sensor intercepts magnetic flux from the magnetization patterns on the recording medium and converts the magnetic flux into electrical signals, which are then detected and decoded.
There are typically a plurality of disks stacked on a hub that is rotated by a disk drive spindle motor. A housing supports the drive motor and head actuator and surrounds the head and disk to provide a substantially sealed environment for the head-disk interface. The head carrier is typically an air-bearing slider that rides on a bearing of air above the disk surface when the disk is rotating at its operational speed. The slider is maintained in very close proximity to the disk surface by a relatively fragile suspension that connects the slider to the actuator. The spacing between the slider and the disk surface is called the flying height and its precise value is critical to the proper function of the reading and writing process.
The inductive write head and MR read head may be patterned, for example, on the trailing end of the slider, which is the portion of the slider that flies closest to the disk surface. An important factor affecting areal density is the distance between the transducer and the recording surface, referred to as the fly height. It is desirable to fly the transducer very close to the medium to enhance transition detection. Some fly height stability is achieved with proper suspension loading and by shaping the air bearing slider surface (ABS) for desirable aerodynamic characteristics. To achieve such results, the slider may be biased toward the disk surface by a small spring force from the suspension, or “self-loaded” to the disk surface by means of a “negative-pressure” air-bearing surface on the slider.
Another important factor affecting fly height is the slider's resistance to changing conditions. An air bearing slider is subjected to a variety of changing external conditions during normal operation. Changing conditions affecting fly height include, for example, change in the relative air speed and direction, and variations in temperature. If the transducer fly height does not stay constant during changing conditions, data transfer between the transducer and the recording medium may be adversely affected. Fly height is further affected by physical characteristics of the slider such as the shape of the ABS. Careful rail shaping, for example, will provide some resistance to changes in air flow.
As can be envisioned, it is desired to minimize variation in head clearance or flying height. However, it is becoming increasingly more difficult to achieve this lower fly height due to inherent limitations of slider and media process consistency. Improved slider designs are therefore desired that can account for these inherent process limitations while providing very low and stable flying heights. No solution provides improvement to altitude, protrusion and speed performance as much as a three-step air bearing surface design. Yet, a three step air bearing in itself is not sufficient to provide the required fly height sigma and roll stiffness.
It can be seen that there is a need for a method and apparatus for providing a three step air bearing with improved fly height performance.